A number of laboratories have reported the unmasking of cell antigens with neuraminidase treatment. However, we have been unable to demonstrate any enhanced immunogenicity or antigenicity of L5178Y/F tumor cells after treatment with neuraminidase (VCN). This conclusion was based on the lack of any difference in survival time of mice primed or challenged with VCN treated tumor cells relative to results with untreated cells. In addition, VCN was not able to cause a loss of radioactivity in mice injected with tumor cells labeled with IUDR 125. Since loss of radioactivity in mice bearing the IUDR 125 labeled cells was not altered by treatment of the tumor cells, it appears that such treatment did not alter the host's ability to recognize such cells. We will conduct additional studies to insure that the parameters used to date as a measure of antigenicity and immunogenicity were adequate. We will therefore use the in vitro migratory inhibitor factor (MIF) test and additional in vitro tests to further examine the effects of neuraminidase on alteration of antigenicity.